Perform a Clean Install of OS X Lion on Your Mac

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Perform a Clean Install of OS X Lion on Your Mac

OS X Lion Installer
You can still create a clean installation of Lion on an internal drive, a partition, an external drive, or a USB flash drive. Screen shot courtesy of Coyote Moon, Inc.

Apple has made the installation process for OS X Lion slightly different than it was for previous versions of the operating system. But even with the differences, you can still create a clean installation of Lion on an internal drive, a partition, an external drive, or a USB flash drive.

In this step-by-step article, we're going to look at installing Lion on a drive or partition, either internally on your Mac or on an external drive. For those of you who want to create a bootable USB flash drive with Lion installed, check out the guide: Create an Emergency Mac OS Boot Device Using a USB Flash Drive.

What You Need to Install Lion

  • The Lion installer: The Mac App Store is the only place to get a copy of Lion. You must have Snow Leopard (OS X 10.6.6) or later installed in order to use the Mac App Store. This seems to be the only reason you must have Snow Leopard installed. Once you purchase Lion and download the installer, you can copy the installer to any Mac that meets the minimum hardware requirements and install Lion, even if that Mac isn't running Snow Leopard. The Lion installer will be downloaded to your /Applications folder, and is called Install Mac OS X Lion. The installer is just under 4 GB in size.
  • A drive or partition with at least 8 GB free: You can install Lion on any internal drive, including SSDs (Solid State Drives). In addition, you can install Lion on any external drive that is connected to your Mac by USB 2.x, USB 3, FireWire 400/800, or Thunderbolt. eSATA-based external drives probably won't work as bootable installation destinations because most add-on eSATA controllers don't currently support booting OS X.
  • 8 GB of free space to install Lion: Apple lists 8 GB as the minimum, but my personal recommendation is a minimum of 60 GB; this assumes you have a second drive somewhere to store user data.
  • 650 MB of free space for Lion Recovery Partition: The Lion installer creates two partitions, one for Lion and one for recovery tools. You can use the Recovery Partition to repair drives, fix permissions, and format drives, as well as reinstall Lion, if needed. The Recovery Partition includes a bootable system with Disk Utility.

With everything ready, let's start the installation process.

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Install Lion - The Clean Install Process

OS X Disk Utility erasing a drive.
You must erase the target drive before you can start the Lion installation process. screen shot courtesy of Coyote Moon, Inc.

To perform a clean install of Lion, you must have a disk or partition available that uses the GUID Partition Table and is formatted with the Mac OS X Extended (Journaled) file system. The target volume should be erased at best; at a minimum, it should not contain any OS X system.

With previous versions of OS X installers, you could erase the target drive as part of the installation process. With the Lion installer, there are two methods of performing a clean install. One method requires you to create a bootable Lion install DVD; the second lets you perform a clean install using the Lion installer you downloaded from the Mac App Store.

The difference between the two methods is that in order to use the Lion installer directly, you must have a drive or partition that you can erase prior to running the installer. Using a bootable Lion install DVD allows you to erase a drive or partition as part of the installation process.

If you wish to use your current startup drive as the target for a clean install, you'll need to the use the bootable Lion install DVD method we outline in the following article:

If you're going to perform a clean install of Lion on a drive other than your current startup drive, then you're ready to proceed.

Perform a Backup

Before you begin the Lion installation process, it's a good idea to back up your existing OS X system and user data. Performing a clean install on a separate drive or partition shouldn't cause any type of data loss with your current system, but stranger things have happened, and I'm a firm believer in being prepared.

At a minimum, make sure you have a current backup. For a bit more protection, make a bootable clone of your current startup drive. You can find the method I use in the following article:

If you would rather use Carbon Copy Cloner, you will find the developer makes older versions of the app available that will work with OS X Snow Leopard and Lion.

Format the Destination Drive

You must erase the target drive before you can start the Lion installation process. Remember that to use the Lion installer as downloaded from the Mac App Store, you must have a working copy of OS X to start the installer from. This means you may need to create a new partition to install to, or resize existing partitions to create the necessary space.

If you need instructions for adding, formatting, or resizing a drive's partitions, you can find them here:

Once you complete the preparation on the target volume, you're ready to begin the Lion installation.

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Use the OS X Lion Installer

Lion installer selecting a target for installtion.
A list of available disks that you can install Lion on will appear. Scroll though the list and select the target disk. Screen shot courtesy of Coyote Moon, Inc.

You're ready to start a clean install of Lion. You have performed any necessary backups, and erased a target volume for the installation. Now it's time to start the actual installation process.

  1. Before you start the Lion installer, close all other applications that may be currently running on your Mac.
  2. The Lion installer is located at /Applications; the file is called Install Mac OS X Lion. The download process from the Mac App Store also created an Install Mac OS X Lion icon in your Dock. You can start the Lion installation process by clicking the Lion installer Dock icon, or double-clicking the Install Mac OS X Lion application in your /Applications folder.
  3. The Install Mac OS X window will open. Click the Continue button.
  4. Scroll through the terms of use, and click the Agree button.
  5. A drop-down pane will appear, asking you to agree to the terms of use. Click the Agree button.
  6. The Lion installer assumes you want to install Lion on the current startup drive. To select a different target drive, click the Show All Disks button.
  7. A list of available disks that you can install Lion on will appear. Scroll though the list and select the target disk; this should be the disk you erased in the earlier step.
  8. Once the target disk is highlighted, click the Install button.
  9. The installer needs your admin password to begin the installation process. Enter the appropriate user name and password, and then click OK.
  10. The Lion installer will copy the necessary files to the target disk. Once copying is finished, you will be asked to restart your Mac. Click the Restart button.
  11. After your Mac restarts, the installation process will continue. A progress bar will display, along with an estimate of the time it will take to complete the installation. Installation speed ranges from 10 to 30 minutes.

Note: If you have multiple displays connected to your Mac, be sure to turn all of them on before you begin the Lion installation process. The installer may display the progress bar on a display other than your usual main screen; if that display isn't on, you'll wonder what's going on.

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OS X Lion Setup Assistant Completes the Install

OS X Lion Desktop
Once you complete the installation process the OS X Lion desktop will be displayed. Screen shot courtesy of Coyote Moon, Inc.

Once the installation of OS X Lion is complete, your Mac will display a Welcome window. This marks the start of the registration and setup process for Lion. After just a few more steps, you'll be ready to use Lion.

  1. In the Welcome window, select the country or region where you use your Mac, and click Continue.
  2. A list of keyboard styles will display; select the type that matches yours and click Continue.
  3. Migration Assistant

    The Migration Assistant will now display. Because this is a clean install of OS X Lion, you can use the Migration Assistant to transfer data from another Mac, a PC, Time Machine, or another disk or partition on your Mac.
    I prefer not to use the Migration Assistant at this point, opting instead for a clean installation of Lion. Once I know Lion is installed and working correctly, I then run the Migration Assistant from the Lion installation to move any user data I need to the Lion disk. You can find the Migration Assistant in the/Applications/Utilities folder.
  4. Select "Don't transfer now" and click Continue.
  5. Registration

    Registration is optional; you can simply click through the next two screens if you wish. If you do fill in the registration information, some of the applications you'll be using in Lion will be pre-populated with appropriate data. Specifically, Mail and Address Book will already have your primary email account information partially set up, and Address Book will have your personal entry already created.
  6. The first of the registration screens asks for your Apple account information; enter the email address and password, as requested. Not sure what your Apple account is? For most individuals, it will be the account they use at the iTunes Store or the Mac App Store. If you have forgotten your password, you can enter just your email address. This will help in setting up Mail later on.
  7. Enter your Apple account information, and click Continue.
  8. The registration window will display. Enter the requested information, if you wish. When you're finished, or if you prefer not to register, click Continue.
  9. Administrator Account

    Lion requires at least one administrator account to be set up. You can use the administrator account to perform most Lion housekeeping tasks, to create additional users, and to install any applications that require administrator privileges.
  10. Enter your full name. This will be the administrator account name.
  11. Enter your shortname. This is a shortcut name used for the administrator account, and the name of the account's home directory. Shortnames cannot be changed, so be sure you're happy with the name you enter; you'll be living with it for a long time.
  12. Enter the password you wish to use, along with any additional information requested, and then click Continue.
  13. You can associate an image or picture with the account you're creating, if you wish. If you have a web cam connected to your Mac, you can snap a picture of yourself to use. You can also choose one of many pictures already installed in Lion. Make your selection, and click Continue.
  14. Learning to Scroll

  15. The Lion Setup Assistant is just about done. The final step shows you how to use the new touch-based gesture system in Lion. Depending on the type of touch-based input device you have (Magic Mouse, Magic Trackpad, or integrated trackpad), you will see a description of how to scroll. Follow the instructions to scroll down through the text area, and click the Start Using Mac OS X Lion button.
  16. Just One More Thing

    That's it; you can start exploring Lion. But before you head off, use the Software Update service to ensure that you have all the latest patches, device drivers, and other undercover goodies your Mac may need to perform at its best.
  17. From the Apple menu, select Software Update, and then follow the onscreen instructions.
  18. Once Software Update has finished, you're ready to take your new installation of Lion for a spin.

Now that OS X Lion is installed you should take a bit of time and check that everything is working as expected. Once satisifed, you can use Software Update, located under the Apple menu to update your OS X Lion installtion to the latest version of the Lion OS.